1. Field of the Invention
The present invention relates to a two-stage type torsion pivot hinge, and especially to a pivot hinge mounted on a set of foldable electronic equipment to allow a screen to have a larger supporting force when it is opened and get its working angular position, while only a smaller force is needed for opening, but a larger force is needed for closing to prevent impact.
2. Description of the Prior Art
On a set of foldable electronic equipment such as a notebook, pivot hinges must be used to connect a screen to the main body of a key board, so that the screen can be rotated taking the pivot hinges as a center for opening or closing relative to the key board.
The torsion force provided for a common pivot hinge is constant when in opening at any angular position, that is, a user shall use the same force to rotate the screen, overly large torsion force will render uneasy of opening, while overly small torsion force will make the screen be subjected to falling down, and to resulting impact in closing.
Particularly, following evolving of computer operational systems, it is the probable coming tendency of development to directly install touch controlled displaying screen in a notebook for the convenience of use of a user. Therefore, for the purpose of meeting the coming tendency, it is necessary to innovate a two-stage type torsion pivot hinge, in order that there is a larger supporting force for a screen when it is at a position to be opened, so that a user is convenient to operate the touch controlled screen without having the screen being shaken or falling down.
In a preceding U.S. Pat. No. 7,124,473 titled “HINGE FOR A NOTEBOOK COMPUTER”, a two-stage type torsion pivot hinge was provided. The case disclosed a pivot hinge to be mounted on a notebook and having a function of opening a screen in two stages, the pivot hinge includes a fixing seat fixed on the main body of the notebook, and is provided thereon with a passage and an barrel in communicating therewith, and a pintle in connecting with the screen of the notebook is provided in cooperation with the passage with shaft, the shaft is provided thereon in turn with a first tube, a sleeve and a second tube, the lower sides of the first and the second tubes are fixed in the barrel, while the upper sides of the first and the second tubes are mounted in the passage, the sleeve is provided in the passage and are kept suitable tightness against the shaft, the two lateral sides of the sleeve are provided with arc shaped protruding sheets, the front end of one side of the first tube is provided with a first stop, and the tailing end of one side of the second tube is provided with a second stop; when in use, the first stage opening of the screen goes to about 45 degrees, mean time the main body will not be lifted together, while the second stage opening of the screen goes to further suitable opening degree for the convenience of using by the user.
The preceding U.S. Utility Patent is provided only for the convenience of opening by a user, and only is provided with a sleeve between two tubes, such design is hard to meet the requirement for a larger supporting force for a touch screen, and has no design for limitation of the maximum opening degree; hence there is still necessity for improvement to meet the requirement of a touch screen.